Transformers, choke coils and all similar devices, as well as stampings used therefor



3,069,642 VICES, AS

E. LEKENS Dec. 18, 1962 TRANSFORMERS, CHOKE COILS AND ALL SIMILAR DE WELL AS STAMPINGS USED THEREFOR Filed July 31, 1958 2 Sheets-Sheet 1 Dec. 18, 1962 E. LEKENS 3,

TRANSFORMERS, CHOKE 0011.5 AND ALL SIMILAR DEVICES, AS WELL As STAMPINGS USED THEREFOR Filed July 31, 1958 2 Sheets-Sheet 2 United States Patent 3,069,642 TRANSFORMERS, CHOKE COILS AND ALL SIMI- LAR DEVICES, AS WELL AS STAMPINGS USED THEREFOR Emile Lekens, Kapelstraat 197, Aartselaar, Belgium Filed July 31, 1958, Ser. No. 752,348 3 Claims. (Cl. 336211) The invention concerns transformers, and more particularly single phase transformers, choke coils and similar devices.

It is a well known fact, that for numerous technical applications, industry requires such devices to become smaller and smaller, without prejudice to their electromagnetic qualities or to their cost price. As example, we can for instance state the industrial construction of ballast coils for fluorescent lamps.

The improvements, subject of the present invention, not only provide for a considerable reduction in the overall dimensions of transformers, choke coils and similar devices, but also ensure a better use of the available space, as well as a better efiiciency, permit to reduce the quantity of metal used for a given winding and, in certain cases, provide for a considerable simplification of construction and of the tools required for industrial production.

These improvements are chiefly characterized by the fact, that the core of these transformers, more particularly single phase transformers, choke coils and similar devices, is designed in such a way as to have a greater width on leaving the coil, respectively on the outside of same, so that the magnetic circuit is shortened as compared to that of an equivalent core for a similar winding. This same fundamental principle can be applied to transformers as well as to choke coils.

In a particularly favourable application of these improvements, more specially for single phase transformers, the stampings used for building up the core have an extra characteristic, inasmuch as they have a cross section of constant area. These improvements can be put into practice by using cut-out and bent stampings, or by using packs of stampings superposed in different planes, or further by using parts of any particular shape assembled in such a manner as to fulfill the new conditions of the fundamental core, which is the main subject of the invention. On the other hand, the latter also relates to various dispositions and shapes of stampings, the characteristics of which will be more clearly shown in the non limitative examples described in detail below, reference being made to the appended drawings of which:

FIGURE 1 gives a very simple perspective sketch of a transformer of the usual type;

FIGURE 2 gives a corresponding very simplified perspective sketch of a transformer improved according to the invention and using the same windings as those of FIGURE 1;

FIGURE 3 gives a schematic front view of the example of FIGURE 1;

FIGURE 4 gives a schematic front view of the example of FIGURE 2;

FIGURE 5 gives a schematic side view of the example of FIGURE 1;

FIGURE 6 shows a schematic side view of the example of FIGURE 2;

FIGURE 7 shows the spread-out surface of a characteristic stamping for the construction of a core according to the invention;

FIGURE 8 shows a side view of the stamping shown in FIGURE 7;

FIGURE 9 shows the stampings of FIGURES 7 and 8 after having been folded;

FIGURE 10 is a side view of the folded stampings of FIGURE 9;

FIGURE 11 is a perspective view of the layout of the stampings forming the core of a choke coil;

FIGURE 12 is a front view of the layout of FIG- URE 11;

FIGURE 13 is a cross section according to line XIII-XIII of FIGURE 12.

In FIGURES 1 to 6, 1 indicates the windings, 2 the core built according to the classical design and 3 the core built according to the present invention.

So as to comply with the two fundamental principles of the invention, stampings cut, shaped and bent as shown in FIGURES 7 to 10 can be used.

Each stamping is originally of rectangular shape of length L and width L and has been cut so as to form a strip 4, of length L" and width L, at one end, the latter being smaller than the original width L' of the stamping. The thickness of strip 4 can be doubled by attaching a small plate 5 to it, for instance by means of solder. This small plate may be the waste of the original stampings. Next, the thus shaped stamping is bent four times in the same direction and according to the parallel lines AA, B-B, C-C, DD, so as to end up in the shape shown in FIGURE 9, wherein we can recognize aforesaid strip 4 with its lining 5, ledge 6, top wall 7, back wall 8, bottom 9 and ledge 10. The lower edge of aforesaid lining 5 is engaged behind aforesaid ledge 10. Such stampings are produced in progressively varying sizes, in order to be able to assemble them in packs as shown schematically in FIGURES 2, 4 and 6.

By mere comparison of the dimensions it is easy to see, that in the case of a single phase transformer for instance, the bulk for given windings will be considerably lessened when constructed according to the invention, the length of the magnetic path being simultaneously reduced. Merely as an indication, the dimensions of the construction according to FIGURE 4 have been carried over and marked in FIGURE 3. It is also easy to seefor instance in FIGURE 6that better use is being made of the available space and that lost spaces such as 11 and 12, shown schematically in FIGURE 5, have been recovered.

The same advantages can be derived from the use of stampings of very different shapes, but perfectly fulfilling the fundamental principles of the invention. For

instance, the magnetic core can be made up of packs of specially shaped stampings which are assembled in different planes, superposed and solidly held together as shown in FIGURES ll, 12 and 13. In the schematically represented example, a first pack 13 makes up the central core of the windings 1, on either side of which two packs of stampings 14-15 are located, the latter stampings being wider and slightly higher than those of pack 13 and fitted in planes which are perpendicular to that of the latter. Packs 14-15 are bridged over by pack 16 which also determines the airgap 17. Finally the lower edge of aforesaid packs 1415 is joined by a last pack of stampings 18. In order to satisfy the fundamentals of the invention it is necessary and sufficient, that the magnetic circuit in the core be smaller than that of a choke coil built in the usual manner around the same windings, which is fairly easily obtained. Experience has proved moreover that, besides the fact that dimensions are considerably reduced, production is sim plified and the tooling less complicated and cheaper.

It is quite obvious that transformers according to this design and construction can also be used as ballast coils for luminescent or fluorescent lamps, the desired dispersion being provided accordingly.

It is also quite obvious, that devices built in accordance with the invention can eventually be completed by the addition of the usual accessories and can be built into housings, which however will have the advantage over the current type of being considerably smaller and consequently of taking-up much less space.

The invention applies to transformers, choke coils and similar devices the cores of Which possess the fundamental characteristics of the invention, as Well as to all stampings, ,or packs of stampings, specially shaped and prepared to make-up cores according to the principles of the invention.

What I claim is:

1. An inductive apparatus of the character described comprising a core formed of an intermediate leg, two side legs substantially equally spaced from opposite sides of said intermediate leg, and top and bottom legs extending transversely and at right angles to said first mentioned legs, a coil embracing only said intermediate leg, each of said legs being formed of a plurality of stacked laminations of sheet magnetic material the intermediate ,leg having a Width substantially less than the Width of any of the other legs, the intermediate leg also having a stacked depth greater than the stacked depth of any of the other legs, and the cross-sectional area of the intermediate leg being substantially double that of any of the other legs, the cross-sectional area of said other legs being substantially equal.

2. An inductive apparatus of the character described comprising a core formed of two core members, each core member being formed of a plurality of nested elements, each element formed of sheet magnetic material shaped into a generally rectangular tubular section, each of said tubular sections having one side of substantially reduced width and of greater thickness than any of the other sides, the cross-sectional area of said one side being substantially equal to the cross-sectional area of any one of the other sides, said tWo core members being arranged with the sides of reduced Width in juxtaposition, and a coil embracing said last mentioned sides.

3. The invention as defined in claim 2 in which the side of reduced Width has secured thereto a lamination of magnetic material substantially coextensive in area With said side.

References Cited in the file of this patent UNITED STATES PATENTS 20 2,307,612 Westendorp Jan. 5, 1943 2,582,351 Olson Jan. 15, 1952 2,827,614 Strecker Mar. 18, 1958 FOREIGN PATENTS 7,856 Great Britain of 1889 563,517 Great Britain Aug. 17, 1944 UNITED STATES PATENT UEFICE CERTIFICATE @F EORRECTION Patent N00 3,06%642 December 18 1962 Emile Lekens It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In. the heading to the printed epecificetiolri between. lines 6, and 'K insert the following:

Claims priority application Belgium J1me 26 1958 Signed and sealed this 4th day of June 1963c,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents UNITED STATES FATENT UIFEECE @ER'HHQATE @F @UREEUHN Patent N00 3,,O69 o42 December 18 1962 Emile Lekens It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In. the heading to the printed epecifieation between lines 6 and 7 insert the following:

Claims priority applieatien Belgium June En 1958 Signed and sealed this 4th day of June 1963.,

(SEAL) Attest:

ERNEST w. SWIDEE. DAVID MUD Attesting Officer Commissioner of Patents 

